Six component zoom lens

ABSTRACT

A 6-component zoom lens for use between fixed conjugates at magnification ranging from 1:1.02 to 1:0.615. The two outermost components and one inner component are movable relative to the remaining components to vary the focal length of the lens as it is moved between conjugates to vary the image magnification. The inner movable component helps to maintain a flat field over the entire magnification range.

United States Patent Lin Oct. 14, 1975 [54] SIX CONIPONENT ZOOM LENS 3,865,470 2/1975 McCrobie et a] 350/184 I W L Arl lf. [75] nventor al Mm Cal Primary Examiner-John K. Corbin [73] Assignee: Xerox Corporation, Stamford, Attorney, Agent, or FirmRobert .1. Bird Conn. 22 Filed: on. 17, 1974 [57] ABSTRACT A -component zoom lens for use between fixed con- [211 Appl 515766 jugates at magnification ranging from l:l.02 to 1:0.615. The two outermost components and one [52] US. Cl 350/184; 350/215 inn r ompon n re movable relative to the remain- [51] Int. Cl. G02B 15/16 ng omponen s to vary the focal length of the lens as [58] Field of Search 350/184, 186 i i mov betw en conjugates to vary the image magnification. The inner movable component helps to [56] References Cited maintain a flat field over the entire magnification UNITED STATES PATENTS range' 3,687,522 8/1972 Lynch et a] 350/184 1 Claim, 1 Drawing Figure US. Patent Oct. 14, 1975 1 SIX COMPONENT ZOOM LENS BACKGROUND OF THEINVENTION This invention relates to variable magnification or zoom lenses, and more particularly to such a lens for use between fixed conjugate planes, as for example in a photocopying apparatus.

The lens disclosed herein is an improvement on that disclosed in copending application Ser. No. 393,844,

filed by George L. McCrobie and Roscoe .l. Donnel on Sept. 4, l973 now US. Pat. No. 3,865,470.

it is an object of this invention to provide a variable magnification lens for use between fixed conjugate planes in a magnification range of 1:102 to 1:0.615.

Another object of this invention is to provide such a variable magnification lens in which the image field is kept substantially flat throughout the magnification range.

DRAWINGS The drawing is an optical diagram of a variable magnification lens according to the present invention.

DESCRIPTION Referring now to the drawing, a variable magnification or zoom lens is generally indicated at 2. It includes the following six components in optical alignment: a front single lens 4, a doublet 6, a single lens 8, a single lens 10, a doublet l2, and a back single lens 14. Zoom lens 2 is shown disposed between two fixed conjugate planes, an object plane 16. and an image plane 18.

Front single lens 4 is a convex-concave meniscus lens, also designated l. Doublet 6 includes a double 2 convexlens element II and a double concave lens element lll, together forming a convex-concave doublet.

.Single lens 8 is a convex-concave meniscus lens, also designated lV. Single lens 10 is a concave-convex meniscus lens, also designated V. Doublet 12 includes a double concave lens element VI and a double convex lenselement VII, together forming a concave-convex doublet. Back single lens 14 is a concave-convex meniscus lens, also designated VIII.

The entire lens 2 is movable relative to conjugate planes l6 and 18. The front and back single lenses 4 and 14 and the inner doublet 12 are movable lenses relative to the remaining lenses in lens 2. Suitable mechanism is provided for effecting the desired movement but is not a part of this invention and is not shown.

An important feature of this invention is the movement of the inner doublet 12 in conjunction with the outer lenses 4 and 14. Without this feature, and with only the outer elements movable, it was found that image field curvature changed rapidly and image quality deteriorated at the lower magnifications, especially below 120.65. The movement of inner doublet l2 functions to keep the image field substantially flat throughout the magnification range.

The parameters of the lens elements which make up a specific zoom lens 2 are listed in the following table in which N,, is the refractive index at 5876A wavelength and V,, is the dispersion value or Abbe number. Radii (R), thicknesses (T), and spacings (S) are expressed in inches and anegative sign indicates lens radii on centers of curvature on the object side of the lens. S 1 and S indicate respectively spacings from object and image planes to their next adjacent lenses.

REFRACTIVE DlSPERSlON LENS RADlUS(R) THICKNESSU) 'SPAC'INGS INDEX N,, VALUE v,,

1 .02X--23.30386 roux-23.57572 .96X--24. 12286 .s4x--25.94499 .76x--27:275s7 .71x--2s.15127 .65x--29.22256 R,=3.59()28 .6l5X-29.84996 1. T,=.57334 1.60729 5946 1.02x--0.1011x 1.00x--0. 100110 .96X 10320 .x4x--0. 22 .76x--0.20797 .7lX--().2642l .65x--0.35040 .615x-041221 R.,=15.71092 v 11: T2=.68986 1.61405 55.17

R.,=15.0120s 111. T .,=.359s7 l.56l38 45.24

R.;=3.43s79 1v. T.,--.S8942 l.66755 41.93

=.95297 R,= 4.48069 v. T .,=.5ss3s 1.66672 48.42

1.02x -.42503 1.00x .42150 .96X--.4258 .s4x--.43355 .76x--.43500- -continued REFRAC'I'IVE DISPERSION LENS RADIUS(R) THICKNESS(T) SPACINGS INDEX N,,, VALUE V,,

.65X--.39850 .615x-.36247 R 3.29l3l v1. T,,=.55711 1.65016 39.15

R..=9.s1162 v11. 11:.60492 1.511904 53.01

1.02X--.09775 l.()X--.()969() sex-.990 .s4x--.13327 .76X--. 19457 .7lX--.25677 .65X--.3735() .6lX-.47l33 R,.=25.s3312 l.()2X--24.820l7 100x" 55005 96X 99777 .x4x- 11392 .7ox- .68479 .71X--19.717s1 .65X--l8.49627 .6l5X-l7.75l86 What is claimed is: -continued 1. A variable magnification lens for use between Lens Thlck' Slmcmgs d1us ness ctivc sion fixed con ugates and mcluding the followmg compo- (R) (T) index value nents in optical alignment: Na

a first convex-concave memscus lens I; .mxuumszz a second double convex lens element II, .76X--0.20797 a third double concave lens element Ill, 'z iifi'iggig said second and third elements forming a doublet. i5x ij 33 a fourth convex-concave meniscus lens IV, 35 RF157|U93 II. T568986 l.fil4(l5 55.17 a fifth concave-convex meniscus lens V, R|= l5 m308 a sixth double concave lens element VI, 111. I 559117 1.56138 45.24

'1 a seventh double convex lens element VII, f;

3 sa1d sixth and seventh elements for formmg a dou- R,,=3.43879 bl 1v. T .=.5x942 1.66755 41.93

40 R7=5.892()6 an e1ghth concave-convex memscus lens VIII, 95397 said second and third elements and said fourth and v qt ggggs l 6667 8 4 fifth lenses being fixed relative to each other a 'f unit, said first and eight lenses and said seventh and eighth elements being movable relative to said unit, xljgg the entire variable magnification lens being movable .76X--.43500 between fixed con ugates. the parameters of lens radii (R), thickness (T), spac- .65X--.39850 7 mgs (S), refractlve 1nd1ces (N), and dispersion val- R =4 79H] 615x 5 10 ues (V) being 1n accordance with the following v1. T,,=.55711 l.650l6 39.15 table wherein radii, thickness, and spacings are ex- R0291 v11. T,=.60492 l.58904 53.01 pressed 1n inches and wherein end-most spacings R|2= 1() 95O50 are those between an end lens and its correspond- .t= 1.02x--.09775 mg con ugate p ane. 1.00X--.09690 .96X--.990

7 Lens Ra- Thick- Spacings Refra- Dispcrdius ncss ctivc sion (R) (T) Index Value .o15x-.47133 s R,=,=25.s3312 [034330386 v111. R T 28233: 1.65844 50.88 roux-23.57572 7 96x M7786 1.o2x--24.s2017 .84X--25.94499 l.(JOX--24.55005 .76X--27.27587 X48 Mp7 .96X--..3.99777 65 .84X--22.11392 R.=3.5902s .6l5X-29.84996 ggfigg? I. T,=.57334 1.60729 59.46 7

R. 22l9756 .6SX-l8.496..7 I S .6l5X-l7.75l86.

l.02X--0. l0] l8 I.OOX--(). 10080 

1. A variable magnification lens for use between fixed conjugates and including the following components in optical alignment: a first convex-concave meniscus lens I; a second double convex lens element II, a third double concave lens element III, said second and third elements forming a doublet, a fourth convex-concave meniscus lens IV, a fifth concave-convex meniscus lens V, a sixth double concave lens element VI, a seventh double convex lens element VII, said sixth and seventh elements for forming a doublet, an eighth concave-convex meniscus lens VIII, said second and third elements and said fourth and fifth lenses being fixed relative to each other as a unit, said first and eight lenses and said seventh and eighth elements being movable relative to said unit, the entire variable magnification lens being movable between fixed conjugates, the parameters of lens radii (R), thickness (T), spacings (S), refractive indices (N), and dispersion values (V) being in accordance with the following table wherein radii, thickness, and spacings are expressed in inches and wherein end-most spacings are those between an end lens and its corresponding conjugate plane: 